菌剂与钾肥配施对连作魔芋生长、生理代谢和发病率的影响

以安康当地花魔芋为材料进行盆栽试验，研究娄彻氏链霉菌（Streptomyces rochei）菌剂D74与钾肥配施对连作魔芋生物学性状、块茎产量、叶绿素含量、活性氧代谢、渗透调节物质含量及软腐病的影响，为魔芋连作障碍微生物-化学双重修复提供理论依据。结果表明：菌剂与钾肥配施对连作魔芋具有一定的促生防病作用，使魔芋单株块茎鲜质量和生长系数分别较对照显著增加86.7%和85.9%，软腐病病情指数降低 33.0%。配施处理中，钾肥和菌剂分别在促进魔芋块茎膨大和抑制软腐病方面发挥主导作用。菌剂与钾肥配施促进魔芋叶片叶绿素的合成，其叶绿素a及叶绿素(a+b)含量分别较对照显著增加51.0%及34.6%，同时叶绿素a/b及叶绿素(a+b)/类胡萝卜素比值分别提高41.8%及22.2%。配施的菌剂效应对叶绿素合成的促进作用占主导地位。菌剂与钾肥配施显著提高魔芋的诱导抗性，其叶片过氧化物酶活性、可溶性蛋白和可溶性糖含量分别为对照的3.1倍、2.9倍和2.2倍。采用主成分分析法对魔芋相关19个生理生化指标分析得出特征值、贡献率、累积贡献率和主成分载荷矩阵，提取3个主成分（叶绿素b、叶幅和相对防效）综合评价菌剂与钾肥配施对魔芋连作障碍的修复效果。不同施肥处理综合得分高低顺序为：菌剂与钾肥配施>单施钾肥>单施菌剂>不施肥对照。综上所述，娄彻氏链霉菌菌剂D74与钾肥配施能提高连作魔芋产量并降低植株发病率，有效缓解连作障碍。

Effects of Agent and Potassium Fertilizer on Plant Growth,Physiological Metabolism and Disease Incidence in Continuous Cropping of Amorphophallus konjac

This study evaluated the effects of combined application of a biocontrol actinomycete agent(Streptomyces rochei D74) and potassium(K) fertilizer on plant growth,physiological mechanism and disease resistance in continuous cropping of A.konjac.A pot experiment was conducted by use of the local A.konjac variety in Ankang,Shaanxi province,China.The biological characters,tuber yield,chlorophyll content,reactive oxygen metabolism,osmotic adjustment substances,and disease conditions of A.konjac plants were measured at specific growth stages.The results showed that combined application of the D74 agent and K fertilizer obviously enhanced plant growth and disease resistance in A.konjac under continuous cropping.Fresh mass of tuber per plant and plant growth coefficient of the D74+K treatment increased by 86.7% and 85.9%,respectively,whereas the disease index decreased by 33.0%,compared with values of the control.Under the treatment of combined application,K fertilizer and the D74 agent played a positive role in tuber growth and disease resistance separately.Combined application of the D74 agent and K fertilizer increased chlorophyll synthesis in A.konjac plants.Leaf chlorophyll a and chlorophyll(a+b) contents of the D74+K treatment increased by 51.0% and 34.6%,respectively,compared with those of the control.The chlorophylla/b and chlorophyll(a+b)/carotenoid ratios increased by 41.8% and 22.2%,respectively.In particular,the D74 agent played a dominant role in promoting chlorophyll biosynthesis.Combined application of the D74 agent and K fertilizer substantially improved the resistance in A.konjac plants.Leaf peroxidase activity,soluble protein content,and soluble sugar content of the D74+K treatment were 3.1 times,2.9 times and 2.2 times compared with values of the control.Principal component analysis was used to obtain the eigenvalue,contribution rate,cumulative contribution rate,and principle component matrix for a total of 19 indices,therefore, three principal components(chlorophyll b,leaf width,and relative control efficacy) were extracted to comprehensively evaluate the effects of D74 agent and K fertilizer treatments.The comprehensive scores of different treatments were ranked in the following order:D74+K>K>D74>control.These results indicated that combined application of S.rochei D74 and K fertilizer could improve the yield and reduce disease incidence in continuous cropping of A.konjac.